1st Generation 1964 1/2 - 1973 - Questions & general discussions that apply to a specific year > 1966 Mustang

1966 289 A code, auto, with smog, a/c and Autolite 6ZE hot idle compensator

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socalgt:
Would there be a hot idle compensator valve(in a hose) on this car since there already is one in the original Autolite carb?

67350#1242:
I think only 2BBL cars with A/C got the compensator in the hose.   No need for 2 of them.

jwc66k:
I do not believe that any factory 4100 carburetor used on a 66 Mustang had a hot idle compensator built it for A/C use. If compensator was installed, it would be in the PCV circuit.
Jim

69cobrajetrugae2:
The 4100 that I rebuilt has a hot idle compensator.

The application was for a 64 390 PI but it was on a hot 302 in a 65 fastback that we acquired. What a wonderful carburetor!

I ran tests on the compensator and as I recall it opened at 160F to 180F and closed at 130F.  When it opens the compensator causes a vacuum leak right down the center of the carburetor which adds air to compensate for the rich mixture which occurs when an engine is turned off and the fuel changes state in the bowls flooding the engine.  Usually this happens at high altitudes due to less atmospheric pressure and a hill climb and turning the car off at a rest stop so the engine heat sink percolates the fuel.

 Summer vacations for my family always included a stop at Bishop for food and gas and I remember the open hoods and the air cleaner lids removed.

When the car is moving it's unlikely the carburetor inlet will see 160F but with the AC on in traffic tie ups with the draw of the AC compressor and the retarded smog timing, it's possible.  It's also possible that the engine will stall if it is rich to begin with.

 This condition is mistakenly attributed to vapor lock which I think is very rare.  The vapor lock would not stay in the line like a pea, it would want to change state back to a liquid as soon as the vapor cooled slightly and thus free the line.

 An engine with a true vapor lock will present as the car running out of gas, no smell of fuel with the air cleaner removed would be the symptom. After a 30 minutes sit the car would start up and continue running as if nothing happened.

jwc66k:
Again, not factory. It's typical of carburetor rebuild shops to "just have" one rebuilt that will work "just fine" on your 66. The shop then sells your old original for two to three times what you paid for the replacement. Oh, they use your old tag on the replacement. Nice.
Jim

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